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T Cell Memory Takes Shape

Following an immune response, small numbers of memory lymphocytes persist, providing a rapid-reaction force to protect against further infection. This is the basis for vaccination, and understanding how memory cells work will be key to developing more effective vaccines in the future.

Using mice carrying a viral-specific transgenic T cell receptor, Kaech et al. performed a genome-wide profile of CD8+ T cells and correlated this with function and phenotype of these cells, before and after viral infection. Predictably, genes controlling migration, cytokine expression, and cytotoxicity were active during infection. In contrast, transcription of other genes increased only in memory cells that persisted several weeks after viral clearance. Among these were genes associated with cell cycle regulation, response to homeostatic cytokines, and receptor-mediated signals. Thus, precursors for CD8+ memory T cells emerge during the height of a viral immune response, but only later become fully equipped to self-maintain and to respond rapidly to subsequent infection. — SJS